1. Field of the Invention
The invention relates to accessory devices on a stand for apparatuses, especially operating microscopes, which are freely movable within a predetermined space and are freely orientable with respect to their position and their allocation to an object within this space. Such requirements are specifically placed on operating microscopes which are employed in ENT surgery; however, they are used to an increased extent also in the field of neurosurgery and of plastic surgery. Depending upon the respective field of application and the selected set object, it is possible to attach to the actual operating microscope various accessory modules such as an additional observation tube, a photographic connection, a camera etc., in a known manner. In this case, the calibration problems appertaining to the actual observation apparatus (microscope) which do indeed already exist are intensified.
2. Description of the Related Art
EP-A-23,003 discloses a supporting device for an optical observation apparatus in which a plurality of pivotal systems designed as linkage parallelograms permit the mobility of the microscope. In this case, use is made of a displaceable counterbalancing weight for free orientation in space. Moreover, electromagnetic retarder bearings ensure the fixing of the optimal stand setting.
EP-A-23,004 contains a description of an accessory device which is in particular capable of compensating rotational and tilting moments in that the position of the center of gravity of the microscope together with its accessories can be determined, and the equilibrium can be adjusted in accordance therewith.
EP-A-49,261 shows a support for an optical apparatus which exhibits as supporting device a rod system which extends through a ball bearing. The apparatus is secured to one of the ends (the lower end), and a counterbalancing weight is secured to the other (upper) end in such a manner that it is displaceable about three mutually perpendicular axes. This displaceable counterbalancing weight permits a free orientation of the microscope in space.
DE-OS-3,617,751 discloses a microscope unit in which an adjustable counterbalancing weight is used, which permits a balancing of the moment which is created about pivotal and tilting axes and which results from the addition or removal of components or modules.
Furthermore, the Wild company brochure (operating instructions) M2-690-XI.86 of November 1986 discloses an operating microscope stand in which the fine adjustment, i.e. the pivoting and inclination of the microscope, is possible by means of milled knobs and inclination levers on drive linkages.
Finally, the Zeiss brochure W 30-082-d of May 1988 ("Ground stand S 21") discloses the concept of providing, in the case of a linkage arm consisting of supporting arm and spring arm, a weight adjustment accessible from outside for the microscope equipment as well as brakes for an individual setting of the mobility of the linkages and of the upward/downward movement.
The described prior art exhibits the following disadvantages, individually or in combination. An essential disadvantage of all known solutions consists in that the resistance to motion of the pivot arms, even when it is adjustable, necessitates the exertion of a very large force for the upward or downward movement of the microscope. The consequence of this exertion of a large force is that a very precise orientation of the microscope in height is not possible without the additional operation of a focusing drive. This additional operation, in turn, involves an interruption of the work to be carried out under the microscope--for example microsurgery. It can be clearly seen without further ado that delays or interruptions of this type cause great disturbance or are dangerous. A further essential disadvantage of the exertion of this large force is that &:he operator, who himself performs very delicate work, may as a result of the exertion of force to be implemented by him undergo muscular stresses which inhibit or have a disadvantageous effect on the progress of the micro-operation. In quite general terms, it can be stated that an interruption of the operating procedure is involved if the operation must be interrupted for the purpose of an alteration of orientation of the optical apparatus, since, for example, the milled knobs must be operated.
Disadvantages of the aforementioned EP-A-23,003 arise from the required effort which arises upon the exchange of one apparatus for another which has a different weight. This effort is further increased in that the location of the position of the center of gravity and the setting of equilibrium cannot be implemented easily in logical terms and cannot be carried out without complications. Complicated, time-consulting equilibrium settings, which moreover cannot easily be implemented from the point of view of the operating personnel, impede a high degree of flexibility regarding accessories, which nowadays is to be required in modern operating microscopy.